急性大剂量γ射线照射对小鼠外周血淋巴细胞损伤的作用及其机制

Effect and mechanism of acute high dose gamma-irradiation on injury of mouse peripheral blood lymphocytes

目的:已知射线能引起免疫系统损伤,为此观察急性大剂量γ射线照射后小鼠外周血淋巴细胞的凋亡机制及与免疫功能的关系。方法:用原位末端标记、原位杂交和碱磷酶免疫组化技术观察急性大剂量γ射线照射小鼠外周血淋巴细胞凋亡特征,bax,bcl-2和bcl-XL的表达及T细胞亚群的变化。结果:①照射后,白细胞数迅速下降。而淋巴细胞凋亡率持续升高,7d达到峰值,12个月仍未恢复到正常值。照后24h在6～12Gy范围内呈较好的剂量效应关系,≥15Gy照射后凋亡率降低。②6Gy照后24h,淋巴细胞Bax蛋白表达即出现升高,当剂量为12Gy时达到峰值,≥15Gy照射后出现降低;而Bcl-2和Bcl-XL蛋白表达在照后24h明显下降,于12Gy照射后降至最低。Bax和Bcl-2mRNA的表达显示出相似的变化趋势。③照后3d,随照射剂量的增加T细胞及其亚群急剧降低,呈较好的剂量效应关系。结论:≤12Gy照射后细胞凋亡是淋巴细胞的主要死亡方式。照射后Bax的上调及Bcl-XL的下调在急性大剂量照射引起的淋巴细胞凋亡和免疫调控中起重要作用。

AIM:It has been known that irradiation can induce the injury of immune system,therefore the apoptosis mechanism of mouse peripheral blood lymphocytes irradiated by acute high dose γ ray and its relationship with the immune function are to be observed. METHODS:Terminal deoxynucleotidyl transferase mediated dUTP nick end labeling(TUNEL),in situ hybridization and immunohistochemical methods of alkaline phosphatase were used to analyze the apoptosis characteristics,expressions of bax,bcl 2 and bcl XL,and the changes of T cell and its subsets in mouse peripheral blood lymphocytes after acute high dose γ irradiation. RESULTS:① After radiation,the number of white blood cell(WBC) in peripheral blood decreased rapidly,while the apoptosis rate of lymphocytes increased persistently and arrived at the peak on day 7.However,it did not recover to the normal level untill 12 months after radiation.After 24 hour irradiation,the apoptosis rate showed a good dose effect relationship within the range of 6 and 12 Gy,then decreased obviously after ≥ 15 Gy irradiation.② The expression of Bax protein in lymphocytes increased immediately at 24 hours after 6 Gy γ irradiation,and approached to the peak value at 12 Gy,then decreased after ≥ 15 Gy γ irradiation.Meanwhile,the expressions of Bcl 2 and Bcl XL mRNA reduced evidently at 24 hours after γ irradiation,and reached to the lowest values after 12 Gy γ irradiation.Interestingly,the analysis on bax mRNA and bcl 2 mRNA expressions also showed a similar results to the expressions of Bax and Bcl 2 proteins.③ With the increase of radiation doses,T cell and its subsets decreased sharply and showed a better dose effect relationship at 3 days after irradiation. CONCLUSION:It is suggested that apoptosis is the major way of lymphocyte death after ≤ 12 Gy radiation.The upregulation of bax and downregulation of bcl 2 and bcl XL indicate that they play an important role in the lymphocyte apoptosis and immune regulation induced by acute high dose radiation.